The present invention relates to a device for processing a workpiece using a machining center, situated in a working space, in which the workpiece is processed using a tool, the working space being constructed to have a gas stream able to flow through for removing processing residues, and being equipped with a first cross sectional area and a second cross sectional area that is smaller than the first cross sectional area, and is positioned behind the first cross sectional area in the flow direction.
A device of the type named is referred to in German Published Patent Application No. 44 39 114. A machine tool for dry machining of a workpiece has a sectional chamber, in which the workpiece is processed, that is separated by a metal partition. Cuttings that are created are removed from the chamber by supplying gas to this chamber or by exhausting gas from the chamber. The metal partition is tapered in the downward direction, so that the pressure gradient in the sectional chamber is influenced in such a way that an orderly removal of cuttings may occur through the evacuation opening situated in this region. However, cuttings which come about by the metal removal in the region workpiece/tool are not picked up by this flow.
German Published Patent Application No. 197 34 631 A1 refers to a device for cleaning processing residues by using cleaning air. A workpiece to be cleaned is introduced into a working space that becomes narrower as it goes, a suction air stream flowing through the working space, whose flow speed increases within the working space, sucking off the contaminations from the workpiece. For the removal of coarse, heavy cuttings, an extreme narrowing of the working space or a generously dimensioned evacuation device would be necessary. The processing residues created by processing workpieces are not able to be removed by this air stream since the processing takes place in another machine or in a separate housing chamber, which calls for a considerable requirement for different machines.
In German Published Patent Application No. 197 34 628, a method is referred to for removing processing residues in which the machining center of a workpiece is crossed by a directionally guided suction air stream in a tightly sealed encapsulated working space. The working space includes the entire machine tool and is therefore of a considerable size. In order to be able to remove the processing residues in an orderly fashion, it is necessary to have a corresponding suction power, and, connected with that, generously dimensioned exhaust equipment. German Published Patent Application No. 40 02 568 A1 also refers to a method for removing processing residues from a processing space. The processing residues are blown out of a settling region and towards a suction air stream. In the settling region, an exactly to be defined suction air stream is formed by a partial vacuum in the working space. This method is very costly, since a working space, in which the processing machine itself is situated, has to be evacuated.
A further device for sucking off processing residues is referred to in German Published Patent Application No. 196 51 662. To efficiently keep the processing region free from processing residues, the sucked-off air is guided towards a nozzle situated in the processing region by the sucking accessory via a feedback line This device is very costly
German Published Patent Application No. 42 18 247 refers to a device in which a removed material trap housing for cuttings created by the processing is fastened directly to the tool or the spindle. In this case, however, not all the cuttings created are trapped. Besides, different trap housings are required for different tools.
In European Patent Specification No. 51 06 37 and PCT International Patent Application No. WO 93/16 334, a working space is referred to in which an air curtain is created in front of a working space opening by a circulating air stream, and this prevents the inflow of environmental air into the working space. The method does not mention whether or how processing residues are removed.
An object of an exemplary embodiment of the present invention is to provide a device, of the type mentioned at the beginning, by which the removal of processing residues from the working space is substantially improved, without the need to increase the performance of the equipment creating the gas stream.
Thus, according to the exemplary embodiment of the present invention, a device for processing a workpiece is provided in which the working space (or enclosure) has, in the direction of flow of the gas stream, a third cross sectional area positioned behind the second cross sectional area and enlarged with respect to it, and the machining center is situated behind a narrowest cross sectional area of the working space. On account of the design of the working space in the form of a Laval nozzle, the gas flow inside the working space is at first continuously accelerated, specifically until shortly after the narrowest cross section. The maximum speed of the gas flow occurs at that point. In this region the machining center is situated. The processing residues created here, for example the workpiece particles or liquid cooling lubricants, are exposed to the greatest flow speed of the gas stream, so that a greater kinetic energy, compared to that at the inflow speed, may be transmitted to the processing residues. Thereby the removal of the processing residues is made substantially simpler and better. The flow speed of the gas stream is influenced positively, without change in the performance of the equipment generating the gas stream. Since the machining center is positioned in the region where the working space becomes larger again, there is sufficient space for the workpiece and further parts of the device, such as, for instance, a supporting table. The gas stream guided into the working space for removing the processing residues may additionally be used for cooling the tool and/or the workpiece.
Another exemplary embodiment of the present invention is provided by supplying the working space with a arrangement that acts to rotate the gas stream about its flow axis. This puts a spin on the gas stream. Under the influence of the appearing centrifugal forces, the processing residues are removed radially outwards, away from the machining location.
In another exemplary embodiment, the arrangement has a flow-directing element. In this context, the flow-directing element is fixed in the region of an edge section of the working space.
In another exemplary embodiment, the working space has a working space wall having a design which sets the gas stream into rotation about its flow axis, in order to further optimize removal of the processing residues in this manner. This may involve, for instance, spirally shaped grooves in the working space wall. This design is produced in one piece with the working space wall. No additional components have to be positioned in the working space or fastened to the working space wall.
In another exemplary embodiment, the working space has a supply device or a removal device for supplying or removing a gas, the gas being at least partially able to be supplied to or removed from the working space in a tangential manner, and thereby the gas stream may be moved into rotation about its axis of flow. In this case, the flow speed of the gas stream is not lowered by conducting elements or designs in the working space wall.
In addition, in an exemplary embodiment a filtering element may be assigned to the supply device or the removal device. Thereby penetration of undesired environmental influences, such as dust particles, together with the gas stream is effectively avoided. The processing residues may be trapped and appropriately disposed of in the region of the removal device.
In this connection, in an exemplary device according to the present invention, the working space is essentially formed comparably to a Laval nozzle. Thereby, in the regions of different cross sectional areas, exactly predeterminable flow conditions prevail which are usable in optimal fashion for the processing of the workpiece.
In connection to this, according to another exemplary embodiment of the present invention, the position of the machining center in the working space may be set. In this case, the position may be made to follow, for example, the progressive processing of the workpiece, so that the region of the application of the tool is held constantly in the region of the greatest flow speed.
In another exemplary embodiment, the working space is designed or arranged to be at least sectionally transparent, so as to make possible to the operator a visual control of the machining process.